Changes of cortical somatosensory evoked potentials under different levels of ischemia in the spinal cord

Abstract

Objective To provide the theoretical basis for the application of cortical somatosensory evoked potential (CSEP) in monitoring the function of the spinal cord to prevent postoperative neurological dysfunction. Methods Thirty-three New Zealand rabbits were randomly divided into 6 groups: 8 were chosen as control group to eliminate the influence of anesthesia and surgery on the evoked potential; the other 25 were assigned to 5 sub-experimental groups (n=5) according to the artery number being ligatured in the left renal arteries and the spinal arteries. Baseline evoked potential in each group was noted immediately after anesthesia; the CSEP were recorded at different time points (before vascular ligation, 30 min and 2 d after vascular ligation). Motor functions were assessed after narcotic conscious and 2 d after vascular ligation. The specimens were taken for HE staining. Results The latency was not sensitive to spinal cord ischemia and no significant difference of that was found between the experimental groups and the control group (P>0.05); except that, the changes of theamplitudes were very complex and the specificity of motor function was decreased. The amplitude reduced and then gradually restored in the 2, 3 and 4 levels of ligation. The changes of amplitude could indicate the degree of pathological damage in the spinal cord and its motor function. Conclusion Complex amplitude of somatosensory evoked potential can be found in the acute phase of ischemia in the spinal cord. Specificity of motor function is poor resulting from its signal averaging process. Motor evoked potential monitoring in the operation should also be added in the detection of the spinal cord. Key words: Cortical evoked potentials; Motor function; Ischemia in the spinal cord